Blast Wall Research Articles

Pressure-Impulse Diagrams for Blast Loaded Continuous Beams Based on Dimensional Analysis

Pressure-impulse diagrams are commonly used in preliminary blast resistant design to assess the maxima of damage related parameter(s) in different types of structures as a function of pulse loading parameters. It is well established that plastic dynamic response of elastic-plastic structures is profoundly influenced by the temporal shape of applied pulse loading (Youngdahl, 1970, “Correlation Parameters for Eliminating the Effect of Pulse Shape on Dynamic Plastic Deformation,” ASME, J. Appl. Mech., 37, pp. 744–752; Jones, Structural Impact (Cambridge University Press, Cambridge, England, 1989); Li, and Meng, 2002, “Pulse Loading Shape Effects on Pressure–Impulse Diagram of an Elastic–Plastic, Single-Degree-of-Freedom Structural Model,” Int. J. Mech. Sci., 44(9), pp. 1985–1998). This paper studies pulse loading shape effects on the dynamic response of continuous beams. The beam is modeled as a single span with symmetrical semirigid support conditions. The rotational spring can assume different stiffness values ranging from 0 (simply supported) to ∞ (fully clamped). An analytical solution for evaluating displacement time histories of the semirigidly supported (continuous) beam subjected to pulse loads, which can be extendable to very high frequency pulses, is presented in this paper. With the maximum structural deflection, being generally the controlling criterion for damage, pressure-impulse diagrams for the continuous system are developed. This work presents a straightforward preliminary assessment tool for structures such as blast walls utilized on offshore platforms. For this type of structures with semirigid supports, simplifying the whole system as a single-degree-of-freedom (SDOF) discrete-parameter model and applying the procedure presented by Li and Meng (Li and Meng, 2002, “Pulse Loading Shape Effects on Pressure–Impulse Diagram of an Elastic–Plastic, Single-Degree-of-Freedom Structural Model,” Int. J. Mech. Sci., 44(9), pp. 1985–1998; Li and Meng, 2002, “Pressure-Impulse Diagram for Blast Loads Based on Dimensional Analysis and Single-Degree-of-Freedom Model,” J. Eng. Mech., 128(1), pp. 87–92) to eliminate pulse loading shape effects on pressure-impulse diagrams would be very conservative and cumbersome considering the support conditions. It is well known that an SDOF model is a very conservative simplification of a continuous system. Dimensionless parameters are introduced to develop a unique pulse-shape-independent pressure-impulse diagram for elastic and elastic-plastic responses of continuous beams.

Inelastic deformation and failure of partially strengthened profiled blast walls

An integral part of a typical offshore module is the surrounding profiled blast walls that separate the potentially hazardous regions of the topside. Many of the blast walls in operation were designed to resist lower loads than those envisaged today [1] rendering them currently non-functional, thus it is desirable to upgrade their blast resistance in a cost-effective and non-intrusive manner. One proposal is to retrofit the existing blast walls partially with centrally located composite patches. This study presents the development of a rapid assessment tool which provides understanding of the effect of a composite patch on the blast resistance of profiled blast walls. The tool is based and is an improvement upon a previous analytical formulation for unstrengthened walls with realistic connection systems [2]. Numerical simulations of a proposed retrofitted wall are performed to gain insight into the failure progression of the wall. Damage in the composite patch is modelled using the Hashin damage model, and the numerical simulations showed that fibre fracture did not occur and that the small amounts of matrix failure occurring at the composite patch edges did not result in significant loss of in-plane stiffness and strength. Based on these observations the rapid assessment tool, analytically formulated to incorporate the effect of the composite patch which strengthens the wall and moves the plastic hinge locations away from the wall centre to the composite-steel edge, is deemed a suitable tool. The assessment tool and the numerical simulations are partially validated by the experimental results presented in [1] for unstrengthened blast walls. The tool runs quickly and provides reasonable predictions for the deformation response of the walls, and enables the user to quickly assess the effect of adding a composite patch. It allows for multiple deformation modes in the panels and the development of plastic hinges at the composite-steel edges and the wall connections, providing a significant advantage over conventional single-degree-of-freedom models. The numerical simulations and the rapid assessment tool give reasonable agreement for different loading regimes, given the anticipated use of the analytical approach.

Modified Quasi-Static, Elastic-Plastic Analysis for Blast Walls with Partially Fixed Support

Blast walls with partially fixed support have been used to limit impacts of pressure due to an explosion. As design criteria, the dynamic response of blast wall systems in terms of their pressure load-displacement relationship is considered. In addition to a complicatedly dynamic analysis, the quasi-static, elastic-plastic analysis is recently an alternative method. However, the pressure load-displacement response of the system with the short connection obtained from the quasi-static, elastic-plastic analysis tends to be over conservative comparing with the response of the previous experiments. Therefore, the model is modified to improve the prediction accuracy. The quasi-static, elastic-plastic model simply consists of two flexural elements connected through an angular spring element. The beam end is supported by the vertical and horizontal spring. The horizontal spring is simulated based on a cantilever beam mechanism and an axial restraint of the connection member. The uncoupled displacement mode shapes are assumed to represent the overall elastic-plastic behavior of the systems. The quasi-static equilibrium equations are determined from the minimum potential energy of the system. The predicted response of the modified analysis is found to better agree with the previous experimental response of the systems with the short connection.

해양플랜트 설비 Corrugated Blast Wall의 폭발 충격응답 인자 특성에 관한 파라메트릭 연구

*The Ship and Offshore Research Institute Pusan National Univer sity, Busan, KoreaKEY WORDS: Explosion 폭발, Corrugated blast wall 파형 방폭벽, Impact response characteristics 충격응답특성.ABSTRACT: More than 70% of the accidents that occur on offshore installat ions stem from hydrocarbon explosions and fires, which, because they involve blast effects and heat, are extremely hazardous and hav e serious consequences in terms of human health, structural saf ety,and the surrounding environment. Blast barriers are integral structures in a typical offshore topside module to protect personnel and safety critical equipment by preventing the escalation of events caused by hydr ocarbon explosions. Many researchers have shown the adequacy of the simple design tool commonly used by the offshore industry for the analysis an d design of blast walls. However, limited information is availa ble for corrugated blast wall design with explosion impact response characteristic s. Therefore, this paper presents a parametric study on the exp losion impact response characteristics of an offshore installation’s stainless steel c orrugated blast wall. This paperalso investigates and recommend s design parameters for the structural design of a corrugated blast wall based on a nonlinear structural analysis of experiential results.교신저자 서정관: 부산광역시 금정구 부산대학로 63번길, 051-510-2415, seojk@pusan.ac.kr본 연구는 2011년 부산에서 개최된 한국해양과학기술협의회 공동학술대회에 발표된 논문을 근간으로 하고 있음을 밝힙니다 .

Behaviors of a Blast Wall According to the Angle of Vee Stiffener

This study has been carried out to investigate the influence of inclined angle of vee stiffener used on blast wall structure. In order to prevent the structural buckling, the vee stiffeners is employed and placed on the compressive region. A higher peak pressure was applied in order to investigate the buckling phenomena on the corrugated panel with vee stiffener. The inclined angle of vee stiffener was varied from 15° to 90°. The results show that an alteration of inclined angle has a considerable effect on the dynamic response of the blast wall structure, the deformed shape and the effectiveness of the stiffener due to the absorbed plastic strain energy. The best inclined angle of the vee stiffener is also determined.

Strengthening profiled blast walls and connections using fibre-reinforced plastics

Blast walls are used to limit the destructive effects of a possible gas explosion in an offshore platform by separating the modules from one another. Owing to inadequate blast-resistant capacity of existing blast wall connection systems, strengthening of these structures is required. One approach to solve this issue involves the use of fibre-reinforced plastic composites. In the present study a method has been proposed for optimal strengthening of blast walls and their connections using composite patches. The scheme presented for strengthening blast walls is based on a single parameter used in buckling of plates made of round-house materials and in relation to connections the scheme considers desirable support characteristics. A typical hybrid (steel–composite) system has been analysed both statically and dynamically. Energy absorption capacities of strengthened and unstrengthened systems have been compared and it was observed that increase in the energy absorption capacity is possible provided that there is no damage to the composite patch in fibre breakage mode. This increase is accompanied by large forces being exerted to supporting structures and their vicinity on the profile, which may trigger tearing failure mode. Strengthening patches do not contribute to the energy absorption capacity when there is fibre failure. This is mainly due to the more pronounced opening of connections in a blast load scenario compared to a similar static loading scenario.

조선 해양 구조물용 강재의 소성 및 파단 특성 IV: 고온 기계적 물성치에 관한 실험적 연구

This is the fourth of a series of companion papers dealing with the mechanical property reductions of various marine structural steels. Even though a reduction of the elastic modulus according to temperature increases has not been obtained from experiments, high temperature experiments from room temperature to revealed that initial the yield strength and tensile strength are both seriously degraded. The mechanical properties obtained from high temperature experiments are compared with those from EC3 (Eurocode 3). It is found that the high temperature test results generally comply with the prediction values by EC3. Based on the prediction of EC3, time domain nonlinear finite element analyses were carried out for a blast wall installed on a real FPSO. After applying the reduced mechanical properties, corresponding to to the FE model of the blast wall, more than three times the deflections were observed and it was observed that most structural parts experience plastic deformations exceeding the reduced yield strength at the high temperature. It is noted that a protection facility such as PFP (passive fire protection) should be required for structures likely to be directly exposed to fire and explosion accident.

Blast Walls for Structural Protection against High Explosive Threats: A Review

This paper presents a review of research into the performance of blast walls in providing protection against the damaging effects of a blast wave generated by the detonation of a quantity of high explosive. Explosive sources might be military weapons such as aerially-delivered bombs or, more likely in the context of the current world situation, improvised explosive devices such as might be deployed by terrorist organisations. The paper reviews studies concerned with how blast walls achieve structural protection with particular reference to the importance of the blast wall's location relative to the threat and the asset that is to be protected. The question of what damage a blast wall might sustain, while still retaining its protective capabilities, is also discussed. The paper presents examples of both ‘permanent’ and ‘temporary’ blast wall designs and constructions used by both military and civilian organisations.

Large-scale hydrogen deflagrations and detonations

Large-scale deflagration and detonation experiments of hydrogen and air mixtures provide fundamental data needed to address accident scenarios and to help in the evaluation and validation of numerical models such as the AutoReaGas code (used by Mitsubishi Heavy Industries, Ltd). Several different experiments of this type were performed. Measurements included flame-front time of arrival (TOA) using ionization probes, blast pressure, heat flux, high-speed video, standard video, and infrared video. The large-scale open-space tests used a hemispherical 300 -m 3 facility that confined the mixture within a thin plastic tent that was cut prior to initiation of a deflagration. Initial homogeneous hydrogen concentrations varied from 15% ( ∼ 3.7 kg ) to 30% ( ∼ 7.3 kg ) . An array of large cylindrical obstacles was placed within the mixture for some experiments to explore turbulent enhancement of the combustion using objects similar in scale to what might be found at a refuelling station. All tests were ignited at the bottom center of the facility using either a spark or, in one case, a small quantity of high explosive to generate a detonation. Spark-initiated deflagration tests were performed in a 1/5-scale tunnel using homogeneous hydrogen mixtures to compare against similar tests performed in the open space. Several experiments performed in the 1/5-scale tunnel released 0.1 and 2.2 kg of hydrogen into the tunnel with and without ventilation to represent, respectively, a release from a fuel cell vehicle or the storage cylinder on a hydrogen transport. For some tunnel tests, obstacles representing vehicles were used to investigate turbulent enhancement. A test was performed to investigate any enhancement of the deflagration due to partial confinement produced by a narrow gap between aluminum plates, similar to gaps that might be found between equipment in a hydrogen processing facility or refuelling station. The attenuation of a blast wave was investigated using a 4-m-tall protective blast wall, such as that which might be placed around a hydrogen production facility, storage yard, or refuelling station to protect surrounding structures. Finally, a large-scale hydrogen jet experiment was performed in which 27 kg of hydrogen was released vertically into the open atmosphere in a period of about 30 s to simulate the bursting of interconnecting piping between large high-pressure storage tanks. The hydrogen plume spontaneously ignited early in the release.

Predicting the effectiveness of blast wall barriers using neural networks

Blast damage assessment of buildings and structural elements requires an accurate prediction of the blast loads in terms of the peak pressures and impulses. Blast loadings on structures have typically been evaluated using empirical relationships. These relationships assume that there are no obstacles between the explosive device and the target. If a blast barrier is used to protect personnel or a structure behind it, the actual blast loading environment will be significantly reduced for some distance behind the barrier. This paper is concerned with an accurate prediction of the area of effectiveness behind the barrier using experimental data and a neural network-based model. To train and validate the neural network, a database is developed through a series of measurements of the blast environment behind the barrier. The principal parameters controlling the blast environment, such as wall height, distance behind the wall, height above ground, and standoff distance are used as the training input data. Peak overpressure and peak scaled impulse are used as the outputs in the neural network configuration. The trained and validated neural network is used to develop contour plots of overpressure and impulse adjustment factors to simplify the process of predicting the effectiveness of blast barriers. The developed model is also deployed in a stand-alone application that is used as a fast-running predictive tool for the blast overpressures and impulses behind the wall.

Accelerated 4D Dobutamine Stress MR Imaging with k-t BLAST: Feasibility and Diagnostic Performance

To prospectively determine feasibility and diagnostic performance (with angiography as reference standard) of k-space and time (k-t) broad-use linear acquisition speed-up technique (k-t BLAST) cine imaging during dobutamine stress for identification of inducible cardiac wall motion abnormalities. The study was conducted according to standards of the Charité and Virchow-Klinikum Ethics Committee. Patients gave written consent. Dobutamine stress magnetic resonance (MR) imaging was conducted in 65 patients (mean age, 63 years +/- 9 [standard deviation]; 49 men) with conventional cine steady-state free precession (SSFP). Accelerated four-dimensional (4D) k-t BLAST single-breath-hold imaging with complete left ventricular (LV) coverage was also performed at rest and during stress. For the cine SSFP and accelerated cine techniques, duration of imaging at rest and LV end-diastolic volume and ejection fraction were assessed. Segmental agreement for resting and inducible wall motion abnormalities was determined. In a subgroup (n = 40), direct comparison between SSFP and accelerated cine was performed for coronary stenosis detection. A paired Student t test was used to assess significance of continuous variables. Pearson correlation was used to test correlation between the techniques. Sensitivity, specificity, and diagnostic accuracy were calculated (standard definitions). For quantitative measurement of agreement, Cohen kappa was applied. For accelerated cine, imaging duration at rest was shortened by 40%. Correlations between cine SSFP and accelerated cine for LV parameters were 135 mL +/- 37 versus 129 mL +/- 31 (r = 0.89) for end-diastolic volume and 59% +/- 8 versus 58% +/- 7 (r = 0.95) for ejection fraction. kappa Values for segmental wall motion at rest and stress ranged from 0.77 to 0.91. Sensitivity, specificity, and diagnostic accuracy for coronary stenosis (>or=50%) detection based on arterial territory were 82%, 87%, and 86%, respectively, for cine SSFP and 82%, 86%, and 85%, respectively, for accelerated cine imaging. Accelerated 4D k-t BLAST wall motion imaging at rest and at dobutamine stress is rapid and feasible; LV measurements were nearly identical between the imaging approaches. Segmental wall motion analysis at rest and at stress show excellent agreement and reliable depiction of myocardial territories supplied by coronary arteries with 50% or more luminal narrowing.

Corrugated panels under dynamic loads

Corrugated panels are commonly used as blast walls on offshore installations, and an assessment of their response to dynamic pressure loads needs to be made during design. Although detailed numerical models are commonly used, simplified models based on spring-mass idealisations, such as Biggs’ method, are still important for preliminary design. Based on an earlier static formulation, the dynamic response of a corrugated panel (as characterised by its central deflection) subjected to a uniformly distributed pressure pulse is analysed. A simplified theoretical method is built up and new transformation factors for panels with straight endplates are derived. The method is calibrated against corresponding finite element and experimental results. Good agreement is achieved.

Experimental investigation of blast wall panels under shock pressure loading

A series of field tests was carried out at the BakerRisk test site in San Antonio, Texas on 1 4 -scale stainless-steel blast panels. The panel design was based on a deep trough trapezoidal profile, with welded angle connections at the top and bottom and free sides. The loading applied to the test panel was a shocked pressure pulse representative of the positive phase of the air blast loading arising from a high-explosive charge. The aim of this work was (1) to show the effect of panel response on the reflected blast loading and (2) to investigate the influence of the connection detail on the overall performance of the panel/connection system under shocked pressure loading. The data were also used to develop appropriate analytical and numerical models for correlation with the test results. Large permanent plastic deformations were produced in the panel without rupture. The work has shown that the connection detail can significantly influence the response and blast resistance of the panel to extreme pressure loading. The results highlight the conservative nature of the design guidance for blast wall design, which limits the deflections to 1 40 th of the height of the blast wall. This in turn should lead to more economical design. The results also concluded that further test work was required to confirm that the panel response had any appreciable effect on the pressure loading.

Validated finite element analysis model of blast wall panels under shock pressure loading

A series of field tests was carried out at the BakerRisk test site in San Antonio, TX, on 1/4 scale stainless steel blast panels. The panel design was based on a deep trough trapezoidal profile with flexible welded angle connections. The loading applied to the test panel was a shocked pressure pulse representative of an air blast. The aim of this work was to investigate the influence of the connection detail on the overall performance of the panel/connection system under shocked pressure loading. The data were also used to develop appropriate analytical and finite element numerical models for correlation with the test results. Large permanent plastic deformations were produced in the panel without rupture. The work has shown that the connection detail can significantly influence the response and blast resistance of the panel to extreme pressure loading. This, in turn, should lead to more economical design.

Deformation and failure of profiled stainless steel blast wall panels. Part III: finite element simulations and overall summary

This three-part article presents the results of experimental, analytical and numerical studies on the response of 1 4 scale stainless steel blast wall panels and connection systems. The panel design was based on a deep trough trapezoidal profile with welded angle connections top and bottom and free sides. The loading applied to the panel was a triangular pulse pressure representative of a gas explosion overpressure. The aim of this work was to investigate the influence of the connection detail on the overall performance of the panel/connection system under pulse pressure loading and to develop appropriate analytical and numerical models for correlation with the test results. Part I reported on the experimental investigations, whilst the analytical modelling considerations were examined in Part II. Finite element analysis, with ABAQUS, was used to simulate the blast wall panel behaviour and is discussed in Part III. Large permanent plastic deformations were produced in the panels without rupture, and localised buckling developed at the centre of the corrugations. The work highlights the importance of correctly modelling the support details and the variation in strength with blast direction (the blast wall panels being stronger in the design direction). The modelling approaches predict a design capacity that is 39% higher than the current design guidance predicts, as a result of modelling the supports and including membrane action.

Scale Testing Of Profiled Stainless Steel BlastWalls

A series of laboratory tests were carried out at the University of Liverpool Impact Research Centre on panels of ¼ scale stainless steel blast walls and on various panel/connection systems. The panel design was based on a deep trough trapezoidal profile with welded angle connections top and bottom and free sides. The loading applied to the test panel was a triangular pulse pressure representative of a gas explosion overpressure. The aim of this work was to investigate the influence of the connection detail on the overall performance of the panel/connection system under pulse pressure loading and to develop appropriate analytical and numerical models for correlation with the test results. Large permanent plastic deformations were produced in the panel without rupture. The work has shown that the connection detail can significantly influence the response of the panel to extreme pressure loading.

Inelastic deformation and failure of profiled stainless steel blast wall panels. Part I: experimental investigations

This three-part article presents the results of experimental, analytical and numerical studies on the response of 1 4 scale stainless steel blast wall panels and connection systems. The panel design was based on a deep trough trapezoidal profile with welded angle connections top and bottom and free sides. The loading applied to the panel was a triangular pulse pressure representative of a gas explosion overpressure. The aim of this work was to investigate the influence of the connection detail on the overall performance of the panel/connection system under pulse pressure loading and to develop appropriate analytical and numerical models for correlation with the test results. Part I reports on the experimental investigations, whilst the analytical modelling considerations are examined in Part II. Finite element analysis, with ABAQUS, was used to simulate the blast wall panel behaviour and is discussed in Part III. Large permanent plastic deformations were produced in the panels without rupture, and localised buckling developed at the centre of the corrugations. The work highlights the importance of correctly modelling the support details and the variation in strength with blast direction (the blast wall panels being stronger in the design direction). The modelling approaches predict a design capacity that is 39% higher than the current design guidance predicts, as a result of modelling the supports and including membrane action.

Inelastic deformation and failure of profiled stainless steel blast wall panels. Part II: analytical modelling considerations

This three-part article presents the results of experimental, analytical and numerical studies on the response of 1/4 scale stainless steel blast wall panels and connection systems. The panel design was based on a deep trough trapezoidal profile with welded angle connections top and bottom and free sides. The loading applied to the panel was a triangular pulse pressure representative of a gas explosion overpressure. The aim of this work was to investigate the influence of the connection detail on the overall performance of the panel/connection system under pulse pressure loading and to develop appropriate analytical and numerical models for correlation with the test results. Part I reports on the experimental investigations, whilst the analytical modelling considerations are examined in Part II. Finite element analysis, with ABAQUS, was used to simulate the blast wall panel behaviour and is discussed in Part III. Large permanent plastic deformations were produced in the panels without rupture, and localised buckling developed at the centre of the corrugations. The work highlights the importance of correctly modelling the support details and the variation in strength with blast direction (the blast wall panels being stronger in the design direction). The modelling approaches predict a design capacity that is 39% higher than the current design guidance predicts, as a result of modelling the supports and including membrane action.

Electrorheological and magnetorheological fluids in blast resistant design applications

The performance of electrorheological (ER) and magnetorheological (MR) fluids under impulsively-applied loads is investigated. The ER fluid device, which is operating in the squeeze flow mode, is tested with four different ER fluids, while the MR fluid device is a commercially available shock absorber in which the flow resistance of the fluid is controlled by a small electromagnetic element. Both devices were tested in an experimental rig, capable of providing fast loading that represents the typical loading of an explosive shock in air or the typical loading of a hydrocarbon type explosion. These devices were seen to exhibit sufficient field-induced damping forces when subjected to various mechanical and electrical inputs and hence, they are capable of providing adaptable fixing characteristics for blast resistant and structural members such as blast walls on offshore platforms. In addition, the performance of the ER fluid device under fast loading could be predicted by a theoretical model based on the assumption of a bi-viscous fluid characteristic, and was found to compare very well with that acquired experimentally.

Novel winding for a gas-insulated transformer

There are numerous operational problems with the technology of oil-filled transformers including their considerable mass and associated civil engineering. In addition, blast walls, acoustic baffles or sufficient space are required to protect surrounding buildings in an urban environment. In an attempt to answer these problems, a 20 kVA, single-phase prototype gas-insulated transformer, that employs atmospheric air as its cooling and insulating medium and uses a novel woven winding, was designed and built. This has clearly demonstrated the feasibility of woven winding, gas-cooled transformers that can operate at an average current density of 2.4 A.mm-2 without the aid of powered cooling systems. Success was due to the use of a novel woven winding comprising a copper warp and a PTFE weft. As a consequence of the improved gas flow through this winding and the absence of any insulating cover on the copper strands, the thermal characteristics have been enhanced to a point where this technology is comparable with that of conventional oil–paper insulated transformers, without the accompanying weight, cost and environmental considerations associated with the latter.